This invention relates to the field of manufacturing of hollow insulation products.
Insulation products are well known as well as their desirable characteristics. Examples of dual wall units of such insulation products are disclosed in U.S. Pat. Nos. 3,646,721 and 3,834,096. As disclosed therein the cavity between the spaced and sealed panels may be evacuated or filled with a dry gas.
Laminating of glass panes is also known. See U.S. Pat. No. 3,852,136 where such a process is carried out under pressure. Frequently, spaced and sealed desirable pane window insulation units are used. The cavity between panes may be filled with a dry atmosphere or evacuated as described in U.S. Pat. Nos. 3,940,898 and 3,990,201, respectively. Other insulating panels, such as disclosed in U.S. Pat. No. 3,245,195 have filled the cavity with certain porous filler materials for increased strength.
Formation of double-walled plastic articles is also known. In U.S. Pat. No. 3,405,019 a vacuum bonding process is disclosed while in U.S. Pat. No. 3,580,762 the spaced panels are joined by spin welding of the product. In production line fabrication of hollow plastic articles it has been the practice to have a heating station adjacent a forming station, but not to continuously form the hollow plastic article as it moves. Examples of such work station production lines are disclosed in U.S. Pat. Nos. 3,462,330 and 3,783,078.
A continuous method of sealing a laminated panel is disclosed in U.S. Pat. No. 3,249,659, but the resulting cavity is not formed under vacuum conditions.